Projectors are used for projecting an optical image by modulating light emitted from a light source according to image information. The projectors may be used for presentations in conferences or the like in conjunction with a personal computer. Also, in response to a desire to view movies or the like, on a large screen at home, this kind of projector may be used for a home theater. However, when someone passes between the projector and the large screen, the light emitted from the light source, such as a metal halide lamp, a high-pressure mercury lamp, or the like, may strike that persons eyes and cause discomfort.